1. Field of the Invention
The present invention relates to a light angle detection device that receives light signals emitted from a light source, such as a remote control transmitter etc. and detects the direction of the light source, a method for the fabrication thereof, and an electronic device employing the light angle detection device.
2. Description of the Related Art
Conventional devices of this kind can be roughly divided into the following three types. The first type is a device, in which a light signal is made incident upon multiple light sensing elements (PDs, etc.) and position sensors (PSDs) through small holes in a light blocking plate; the second type is a device, in which multiple light sensing elements are disposed at a slant and a directionality difference is detected from the respective sensed light intensities; and the third type is a device detecting the distribution of light intensity sensed by position sensors and solid-state image sensing devices (CCDs, CMOS', etc.).
For instance, a first conventional device is disclosed in JP6-241757A (hereinafter referred to as Patent Document 1), JP8-210825A (hereinafter referred to as Patent Document 2), and JP8-340124A (hereinafter referred to as Patent Document 3), in which a light signal is made incident upon multiple light sensing elements and position sensors through small holes in a light blocking plate, the position of incidence of the incident light is detected, and the direction of the light source is obtained based on the position of incidence. Moreover, as disclosed in JP8-264826A (hereinafter referred to as Patent Document 4), multiple light sensing elements are positioned behind a light blocking member, on both sides thereof, such that when a light signal is incident thereon, the position of the shadow of the light blocking member projected onto the light receiving surfaces of the light sensing elements is detected and the direction of the light source is obtained based on the position of the shadow of this light blocking member. In any case, the principle used is the same as that of a sundial, in other words, detecting and utilizing changes in the shadow of a light blocking member or incident light depending on the direction of the light source.
Furthermore, a second conventional device is disclosed, for instance, in JP1-13681A (hereinafter referred to as Patent Document 5) and Japanese Patent No. 3508714 (hereinafter referred to as Patent Document 6), where multiple light sensing elements are disposed such that the directionality of the respective light sensing elements is different, and the direction of the light source is obtained by comparing the light sensing outputs of the light sensing elements.
In addition, a third conventional device is disclosed, for instance, in JP9-49733A (hereinafter referred to as Patent Document 7) and JP6-241757A (hereinafter referred to as Patent Document 8), where a light signal is made incident upon multiple light sensing elements and position sensors through a light receiving lens, the position of incidence of the light signal and the focused light spot configuration are detected, and the direction of the light source is obtained based on the position of incidence and focused light spot configuration. Moreover, as disclosed in JP2007-13536A (hereinafter referred to as Patent Document 9), a light signal is made incident upon a solid-state image sensing device such as a CCD or a CMOS, etc., the pixel with the highest sensed light intensity of the solid-state image sensing device is detected, and the direction of the light source is obtained from the position of this pixel.
However, in the first conventional device (Patent Documents 1 to 4), despite the receipt of the luminous flux of a light signal radially spreading from a remote light source, the light signal was either made incident upon light sensing elements and position sensors through small holes or was blocked optically by a light blocking member and its shadow was detected by the light sensing elements, as a result of which the amount of light sensed by the light sensing elements and position sensors was small, their output levels were extremely low, and the sensitivity of detection was low.
Moreover, in the second conventional device (Patent Documents 5, 6), the luminous flux of the light signal radially spreading from a remote light source was received by the light sensing elements “as is”, as a result of which the light receiving surface area of the light sensing elements had to be expanded in order to raise the light sensing output levels of the light sensing elements, which increased the cost and made the device larger in size. In addition, a high accuracy of positioning was required because the accuracy of detection is to a large extent controlled by the accuracy of light sensing element positioning on the inclined surfaces. In general, in a mechanized manufacturing process, it is extremely difficult to accurately perform positioning relative to inclined surface, although positioning relative to even surfaces can be performed with accuracy. Furthermore, it is evident that the efficiency and accuracy of manufacturing are very poor in case of manual manufacturing.
In addition, in the third conventional device (Patent Documents 7 to 9), a light signal is collected using a light receiving lens and is made incident upon multiple light sensing elements, position sensors, and solid-state image sensing devices, thereby causing their light sensing outputs to rise. However, when multiple light sensing elements were used, the accuracy of detection could not be raised if the number of the light sensing elements was not increased, which increased the cost and made the device larger in size. Moreover, when position sensors and solid-state image sensing devices were used, the unit price of the elements was high and it was impossible to avoid a cost increase.